The present invention relates to a governor for an internal combustion engine, and more particularly to a mechanical governor with low temporary droop for a small engine.
Governors are generally used to regulate and stabilize the speed of internal combustion engines. The mechanical governor generally receives an input indicative of an engine speed and moves an engine throttle to adjust the engine speed. A governor spring affects movement of the throttle such that the governed speed of the engine is determined by the interplay between the movement of the governor speed sensor and the spring force of the governor spring. Typically, the speed sensor causes a non-linear speed sensor force, whereas the governor spring is defined by a substantially constant force. Therefore, the governor spring only substantially counteracts the force of the speed sensor over a very limited range, resulting in an unstable governor in some circumstances.
A typical governor provides continuous adjustment to a throttle or other control member in an effort to maintain a constant engine speed. Droop of a governor allows engine speed to drop when a load is applied to the engine. The amount of droop is a characteristic of a particular mechanical governor, and is determined in part by a spring rate of the governor spring and the tension applied to the control member by the governor spring. Reducing the speed droop by lowering the spring rate of the governor spring may cause the governor to be overly sensitive to small changes in engine load, thus resulting in a less stable engine control. On the other hand, increasing the spring rate makes the governor spring stiffer and more resistant to small changes in engine load, thus making engine reaction sluggish.
In many internal combustion engines, adjusting the engine speed may result in engine hunting or over-compensation. Hunting occurs when the engine overshoots or undershoots the desired speed and is unable to quickly settle at the desired speed. Hunting can be caused by many factors, including the use of springs having light spring rates, sticking or binding between movable parts of the engine and the governor, and the like.